Multichambered steelmaking apparatus and method of steelmaking

ABSTRACT

The invention pertains to the art of ferrous metallurgy, and more particularly, to a multichambered steelmaking apparatus and to a method of steelmaking. A multichambered steelmaking apparatus contains smelting chambers communicating with each other through their upper portions. Process input ports are provided in the chamber side wall, and the smelting chambers are provided with gas-oxygen burners installed on the walls of the smelting chambers facing each other. A method of steel making employs the apparatus in a unique manner. During operation, the smelting chambers are tilted in the direction of the input port and during the discharge of steel they are tilted in the direction of the outlet. During the melting stage carbon monoxide (CO) is afterburned by gas-oxygen burners forming carbon dioxide (CO) in the exit gasses supplied to the gas exhaust system through the coaxial chamber. A portion of a slag from the previous heat is retained.

PRIORITY CLAIM

This application claims priority from PCT/RU99/00478 filed Dec. 9, 1999,which in turn claims priority from Russian Application Ser. No. 99114074filed Jun. 25, 1999.

FIELD OF THE INVENTION

The offered group of inventions pertains to the art of ferrousmetallurgy, and more particularly, to a design of a multichamberedsteelmaking apparatus and to a method of steelmaking using suchapparatus.

BACKGROUND OF THE INVENTION

Known is a multichambered steelmaking apparatus comprising smeltingchambers communicating with each other through their upper portions.Each smelting chamber contains two input ports for charging metal scrapand pouring-in liquid iron (said ports being provided in the front wallof each chamber) and a process port arranged between said input ports. Ahearth of each chamber has an outlet. Embrasure orifices, intended forenabling introduction of oxygen supply tuyeres into the operating area,are provided in the chambers roof. The upper portion of the chambersfront wall, said upper portion being arranged above the thresholdslevel, is provided to be tilted at a predetermined angle relative to thevertical in the direction of a back wall (UA, 9024 A, F 27 B 3/02, F 27D 3/00, F 27 D 3/14, publication of Sep. 30, 1996). The describedapparatus was chosen as a prototype of the offered invention.

The above-described design of apparatus enables mold-less charging ofmetal scrap and direct pouring-in of liquid iron from a ladle throughinput ports. Such design enables the apparatus efficiency to beincreased due to more rapid loading of scrap and liquid iron.

Though the above-described apparatus has certain drawbacks, such as thelack of the front wall strength, too complicated fastening of inputports due to the inclination of the front wall in the direction of theback wall, insufficient metal scrap charging speed, difference of loadsinfluencing the roof from the front and back lines of the apparatus. Allthese circumstances affect the strength of apparatus and reduce theup-to-repair life of apparatus, which generally results in the apparatusoutput decrease. Furthermore, the chamber being stationary, thequasi-thresholds and “combs” must be provided in the input ports and ina process port. The described design properties are necessary to avoidsplash-out of molten metal and slag. Thus, expenditure of crude dolomiteand magnesite powder increases. Consequently, smelting time increases aswell.

DISCLOSURE OF THE INVENTION

It is an object of the present invention to provide a multichamberedsteelmaking apparatus of a simplified design characterized by broadenedtechnological features and high efficiency.

It is another, technical object of the present invention to increasestrength of the apparatus and to simplify design thereof. The presentinvention accomplishes these objects as described below.

A multichambered steelmaking apparatus comprises two smelting chamberscommunicating with each other through their upper portions. Each of saidsmelting chambers contains a roof, a hearth with an outlet arranged onthe side of said smelting chamber back wall, side walls and a front wallwith two input ports and a process port arranged between said inputports, metal scrap charging scoops, oxygen supply tuyeres installed inthe roof, a gas exhaust channel provided with a gas-cleaning system anda chimney. Each of the smelting chambers comprises a tilting device andis provided with capability of tilting in the direction of the front andback walls at an angle of up to 45° relative to its vertical axis,furthermore, the gas-oxygen burners are installed in the roof on theside of the smelting chamber side walls. Each smelting chamber comprisesthree oxygen supply tuyeres and two gas-oxygen burners. The sizes of theinput ports correspond to the sizes of the metal scrap charging scoops.

As far as the smelting chambers according to the invention are providedwith capability of rotating about their horizontal axes, the scrapcharging and liquid iron pouring-in, molten metal discharging andslagging-off processes are simplified. Thus execution ofquasi-thresholds and combs in the process input ports, installation ofpouring-in and discharging chutes is not required as far as whilecharging metalline charge and pouring-in liquid iron as well as duringdischarging the molten metal and slagging-off the tilting of chamberstakes place. The described design feature not only ensures favorableconditions of work in the furnace shop but also enables reduction ofcrude dolomite and magnesite powder expenditure.

The input ports sizes are extended (in comparison with the prototype) upto 3500×2000 mm which leads to considerable speeding-up of scrapcharging and liquid iron pouring-in. The chamber depth according to thepresent invention exceeds the depth of conventional Martin furnaces orconventional multichambered steelmaking apparatuses and makes up notless than 2 m. This feature ensures better metal mixing conditions inthe course of melting.

Installation of 3 blowing oxygen supply tuyeres in the roof of eachsmelting chamber ensures substantial intensification of the oxygen blowin the chamber. Availability of two gas-oxygen burners in each of thechambers ensuring CO gases afterburning, said CO gases being suppliedfrom one chamber into another, intensifies the heating of metallinecharge by said CO gases in a coaxial chamber.

The invention according to the Patent UA 9024 (a prototype) teaches amethod of steelmaking in a multichambered steelmaking apparatus,according to which the following steps are provided: mold-less chargingof metal scrap, pouring-in liquid iron directly into the steelmakingapparatus chamber from a ladle through input ports provided in thechamber front wall, charging of flux, oxygen blow with removal of exitgases into a coaxial chamber in purpose of heating the cold metallinecharge already charged. After heating and melting of the metallinecharge in a first chamber buffing is conducted with intermediaryslagging-off through a process port. Then a new slag is formed and afterthe pure boiling step and processing steel up to a predeterminedchemical composition, the steel is discharged from the chamber.

Major deficiencies in this method are: incomplete use of exit gases heatin purpose of heating metalline charge in a coaxial (cold) chamber,insufficient strength of the lining (since the loaded metalline chargecan damage a hearth welded layer and a hearth lining), insufficientlyhigh scrap charging speed and liquid iron pouring-in speed, which leadsto decrease in apparatus efficiency and ready product output.

It is a technical object of the method claimed herein to increasesteelmaking efficiency, to increase ready product output due to thescrap charging time and iron pouring-in time reduction, to acceleratethe metalline charge heating by means of increasing heat utilizationefficiency, to increase the lining strength.

The above-mentioned object is accomplished as described below.

The method of steelmaking using the above-described multichamberedsteelmaking apparatus according to the present invention includes thefollowing steps: charging a smelting chamber with fireproof powders,metal scrap charging through input ports arranged in the smeltingchamber front wall by means of scoops, pouring-in liquid iron throughthe said input ports, charging of flux, oxygen blow with removal of exitgases to the second smelting chamber for heating the already chargedcold metal scrap and further exhaust gases removal through a gas exhaustchannel into chimneys, heating and melting of the metalline charge,subsequent buffing with intermediary slagging-off through a process portprovided in the front wall between the input ports, formation of a newslag, pure boiling stage, processing steel up to a predeterminedchemical composition and discharging steel, wherein metal scrap ischarged into the smelting chamber in combination with flux and, as thistakes place, while metal scrap and flux charging and liquid ironpouring-in the smelting chamber is tilted in the direction of its backwall at an angle of between 20 and 30° relative to its vertical axis;while intermediary slagging-off the smelting chamber is tilted in thedirection of its front wall and while tapping-off steel the smeltingchamber is tilted in the direction of its back wall at an angle of 45°relative to its vertical axis. Furthermore in the course of thedescribed process the carbon monoxide is underwent afterburning up toCO₂ in the exit gases being supplied to the second smelting chamber inpurpose of heating cold metal scrap. Lime and/or limestone performingthe function of flux can be charged into the smelting chamber. Meanwhilea portion of slag from a previous heat can be retained in the smeltingchamber and oxygen blow intensity is 2.5 nm³/ton per 1 minute, pressurekeeping in the range of between 12 and 15 atmospheres. Big off-sizepieces of scrap having weight of between 15 and 20 tons also can becharged into the smelting chamber.

During metal scrap charging and liquid iron pouring-in the smeltingchamber is tilted in the direction of its back wall at an angle ofbetween 20 and 30° relative to the vertical axis of the furnace whichenables accelerated metalline charge loading directly onto thesteelmaking apparatus hearth through the process input ports. Should thesaid angle of rotation be less than 20°, turning over the scoop withmetal scrap and flux into the apparatus is impossible. Should the saidangle exceed 30°, it could result in the apparatus back wall liningstrength reduction.

The angle of rotation in the direction of the process port during theslagging-off step is 18°. This value is an experimental result; it isoptimum with regard to avoiding molten metal splash-out during theslagging-off stage.

Placing an even layer of flux (lime or limestone having width of between10 and 30 cm) on the surface of the metalline charge which is beingloaded, ensures combined charging of flux and metal scrap, which resultsin solid metalline charge loading time reduction. The oxygen blowintensity is 2.5 nm³/min while pressure being between 12 and 15excessive atmospheres, which ensures intensive metal mixing. As thistakes place, the steelmaking process is accelerated. Also processing oflarge off-size metal scrap pieces becomes possible, due to theintermediary scrap heating as well (the weight of such metal scrappieces can be up to 15-20 tons if compared with pieces processed in theoxygen converter and having weight of 2-3 tons).

The essence of the group of inventions disclosed herein consists in thefollowing. The steel is made in an apparatus having intermediate statusbetween an oxygen converter and a multichambered steelmaking apparatus.The disclosed steelmaking technology using a multichambered apparatussuccessfully combines advantages of converter melting and melting in amultichambered furnace. Similar to the converter process, steelmaking inthe said apparatus is effected without supplying additional fuel, it iscarried out only by using heat of iron impurities burning-out exothermicreactions. Similar to the steelmaking process in a multichamberedapparatus, the disclosed method is divided into two stages. Oxygen blowis being carried out in a “hot” chamber, metal melting process isrunning and hot exit process gases are being supplied into a neighbor“cold” chamber. A cold metalline charge loaded into the “cold” chamberis being heated in this chamber and metalline charge melting process isbeing accelerated. After that the exit gases are removed through the gascleaning system—into a chimney. Carbon monoxide (CO) afterburning in theexit gases ensures quicker heating of metalline charge. Furthermore,exit gases perform a function of a shield in a “cold” chamber andprotect the scorching roof from the impact of the next portion of coldmetalline charge being loaded, thus ensuring constant (i.e. withoutharsh overfall) roof temperature and increasing its lining strength. Itis also worth saying that iron oxides contained in the exit gases arepartially adsorbed by cold metalline charge of the neighbor chamber ofthe apparatus which results in reduction of said iron oxides content inthe exhaust gases being removed through the gas-cleaning system.Furthermore it leads to diminishing of metal losses and increasing readyproduct output. Moreover, afterburning of the carbon monoxide (CO)decreases its removal into the atmosphere and thus has a favorableenvironmental effect.

After heat discharging from the “hot” chamber a metalline charge isloaded into said chamber. This chamber becomes “cold” and the processrecurs.

It is advisable that a certain quantity of slag from the previous heatshould be retained in the smelting chamber. In this event, on the onehand, the slag ensures better protection of a hearth from beating by bigpieces of metal scrap (consequently, the lining strength is increased)and, on the other hand, the process of a new slag formation isaccelerated.

Thus the offered apparatus and method of steelmaking in such apparatuscombine all advantages of the oxygen-converter process and smelting in amultichambered steelmaking apparatus and has another advantages asdescribed below.

In spite of liquid iron use as the main heat-carrier there is apossibility of diminishing expenditure thereof, in comparison with theoxygen-converter process, up to 570-730 kg/ton (while the ironexpenditure in a converter usually keeps within the limits of between860 and 950 kg/ton).

The above-described technological process running in the offeredapparatus is characterized by higher heat utilization efficiency ifcompared with a converter. The said heat utilization efficiency iscalculated as a ratio of the heat portion spent directly for thesteelmaking—to the heat total quantity. The heat-utilization efficiencydoes not exceed 30% in a converter though according to the offeredinvention it reaches 78-90%. Furthermore, higher strength of the liningis ensured (ensuring up to 2500 heats).

Regular discharge of heats (each 35-45 minutes) effected by thesteel-making apparatus ensures favorable conditions for combining saidapparatus with a steel continuous tapping-off apparatus.

BRIEF DESCRIPTION OF THE DRAWING

The essence of the offered invention can be described, by way ofexample, with reference to the accompanying drawing in which:

FIG. 1 is a view of a cross-section of the claimed double-chamberedsteelmaking apparatus;

FIG. 2 is a view of the claimed apparatus from one side during metalscrap charging and liquid iron pouring-in;

FIG. 3 is a view of the claimed apparatus from above.

DESCRIPTION OF THE APPARATUS PREFERRED EMBODIMENT

A multichambered steelmaking apparatus according to the inventioncontains two smelting chambers communicating with each other throughtheir upper portions. Each chamber comprises a hearth 1 with an outlet 2arranged on the side of back wall 3 of the smelting chamber, a roof 4with three oxygen supply tuyeres 5 installed in said roof 4 and withgas-oxygen burners 7 installed in the roof on the side of the chamberside walls 6 and applied in purpose of afterburning CO contained in theexit gases. Two process input ports 9 are provided in the front wall 8,said process input ports having the threshold level of +9400 mm. Aprocess port 10 intended for slagging-off is arranged between theprocess input ports 9. Each smelting chamber has a device 11 enablingsmelting chambers rotation about their horizontal axes. Due to the useof said device 11 the chambers are turned in the direction of the frontor back wall at an angle of up to 45° relative to their horizontal axes,depending on a technical operation to be carried out. The FIG. 2 showssuch a position of the smelting chamber when said chamber has beenturned at an angle of between 20 and 30° in the direction of the backwall 3 during the metal scrap charging by means of the scoops 12 whichsizes correspond to the sizes of the process input ports 9 having awidth of 3500 mm and a height of 2000 mm. Liquid iron is poured into thechamber from a ladle 13 through the process input ports 9. The chamberis provided having a depth not less than 2 m.

DESCRIPTION OF THE METHOD PREFERRED EMBODIMENT

Now an example of the claimed method will be described. This method isbased on the multichambered steelmaking apparatus offered herein.

A smelting chamber of the steelmaking apparatus having a capacity of 250tons is charged with fireproof powders. The smelting chamber is turnedin the direction of its back wall 3 at an angle of between 20 and 30°about the chamber horizontal axis. Metal scrap in combination with fluxis charged into the smelting chamber through the process input ports 9using the scoops 12. The said metal scrap and flux are charged onto aportion of the slag from a previous heat that was retained in thesmelting chamber. After loading of the solid charge and heating thereofduring seven minutes, liquid iron is supplied from the ladle 13 throughthe input ports 9 directly into the chamber without use of a loadingchute. In purpose of liquid iron pouring-in facilitation andacceleration the ladle 13 is provided with a special improved lip. Thechamber is restored in a horizontal position. Then oxygen blow isconducted through three oxygen supply tuyeres installed in the roof.Intensity of such oxygen blow is approximately 2.5 nm³/ton per 1 minuteand pressure is from 12 up to 15 atmospheres. Exit gases coming from theapparatus chamber are underwent afterburning by means of two gas-oxygenburners 7 and then are supplied to the “cold” chamber for heating coldmetalline charge loaded therein. After that the exit gases are removedthrough the gas-cleaners 14 and chimneys 15 through the gas-removalchannel. The draught is ensured to be so strong that in spite ofintensive blow the gases can hardly penetrate into the furnace shop. COafterburning is also carried out in regeneration chambers and in smokeflues.

During melting the metalline charge is heated and melted. Then thechamber buffing with intermediary slagging-off through the process port10 is accomplished. The threshold level of the process part 10 isexecuted at the height of +8900 mm. The width of the port 10 is 1250 mm.In purpose of intermediary slagging-off the chamber is tilted in thedirection of its front, wall 8 at an angle of 18° relative to itshorizontal axis. Then the chamber is restored in horizontal position, anew slag is formed, the steps of pure boiling and processing steel up toa predetermined chemical composition are accomplished. After that thechamber is turned in the direction of its back wall at an angle of 45°about its horizontal axis and steel is tapped off the apparatus throughthe outlet 2 and is supplied to a teeming ladle while the slag issupplied into a dump-cinder car.

The experimental smelting time indices are described with regard to anapparatus having capacity of 250 tons as shown below (by stages):

Charging a steelmaking chamber with fireproof 15 min  powders Scrapcharge 6 min Heating 7 min Liquid iron pouring-in 5 min Oxygen blow,including metal finishing 30 min  Steel tapping-off 10 min  Other steps7 min Total smelting time 80 min (1 hour 20 min)

When apparatus capacity and particular steelmaking conditions vary thesmelting time can fluctuate in the range of between 70 and 90 minutes.Thus the group of inventions claimed herein ensures smelting timereduction by 10-15 minutes. The disclosed technology ensures efficientoperation of each part of apparatus and rhythmical heats dischargingeach 35-45 minutes.

As was mentioned above, a new steelmaking apparatus ensures highstrength of lining (up to 2500 heats) due to “cautious” metalline chargeloading, apparatus scorching roof shielding against cold metallinecharge by process gases coming out of the “hot” chamber, retaining aslag portion from the previous heat in the smelting chamber. The offeredtechnology has an environmental protection effect.

Thus the offered group of inventions ensures high steelmaking efficiency(from 2.0 up to 4.0 millions of tons of liquid steel annually dependingon a furnace capacity), safe personnel work conditions. The offeredapparatus and method are perfect with regard to environmental protectionif compared with a conventional multichambered furnace. Furthermore,they create conditions for steelmaking cost reduction due tosimplification of metal scrap charging and liquid iron pouring-in, steeland slag tapping off which, in its turn, is caused by availability of atilting mechanism in both smelting chambers of the apparatus. Thesteelmaking cost is reduced also due to considerable fuel expendituredecrease, refractory materials, changeable equipment, repair costsreduction.

1. A multichambered steelmaking apparatus comprising: at least twosmelting chambers communicating with each other through their upperportions, each smelting chamber comprising at least a roof, a hearthwith an outlet arranged on the side of a chamber back wall, chamber sidewalls and a chamber front wall with input ports and a process portarranged between said input ports, at least one oxygen supply tuyereinstalled on each said roof, a gas exhaust channel with a gas-cleaningsystem and a chimney, wherein each of said smelting chambers is providedwith a tilting device and means for tilting in the direction of saidfront and back walls at an angle of up to 45° relative to a verticalaxis; and said roof comprising a gas-oxygen burner installed on the sideof each of said smelting chamber side walls.
 2. A multichamberedsteelmaking apparatus, according to claim 1, wherein: each smeltingchamber comprises three oxygen supply tuyeres.
 3. A multichambered steelmaking apparatus, according to claim 1, wherein: said apparatus furtherincludes metal scrap charging scoops; and the sizes of said input portscorrespond to said metal scrap charging scoops.
 4. A method ofsteelmaking in a multichambered apparatus comprising steps of: chargingof a smelting chamber with fireproof powders, metal scrap chargingthrough one of at least two input port arranged in a first smeltingchamber front wall by means of scoops, pouring-in of liquid iron throughsaid input ports, charging of flux, conducting an oxygen blow withremoval of exit gasses into th a second smelting chamber for heating thecharged cold metal scrap and further removing of gasses through a gasexhaust channel into a chimney, heating and melting of the metallinecharge, buffing with intermediary slagging-off through a process portprovided in the front wall between said input ports, executing aformation of a new slag, pure boiling stage, and processing the steel upto a predetermined chemical composition; and discharging the steel,wherein metal scrap is charged into said smelting chamber in combinationwith flux, provided that during the steps of scrap and flux charging andliquid pouring-in the first smelting chamber is tilted in the directionof a back wall at an angle of between 20 and 30° relative to a verticalaxis, while during said intermediary step of slagging-off the firstsmelting chamber is tilted in the direction of its front wall, and whiledischarging said steel the first smelting chamber is tilted in thedirection of the back wall at an angle of 45° relative to said verticalaxis, and furthermore providing that during said step of conductingoxygen blowing carbon monoxide undergoes afterburning in exit gassessupplied to the second smelting chamber for heating cold metal scrap. 5.A method, according to claim 4 wherein said method further includes thestep of: charging lime and/or limestone, performing the function offlux, into the first smelting chamber.
 6. A method, according to claim 4whereinsaid method further includes the step of: retaining a portion ofa slag from a previous heat in the smelting chamber after said step ofdischarging.
 7. A method, according to claim 4 wherein: an intensity ofsaid oxygen blow is 2.5 nm³/ton of steel per 1 minute, a pressure beingin the range of between 12 and 15 atmospheres.
 8. A method, according toclaim 4 wherein: during said step of charging, pieces of scrap,including at least one piece having weight of between 15 and 20 tons,are loaded into the smelting chamber.
 9. A multichambered steelmakingapparatus according to claim 1, wherein each smelting chamber comprisestwo gas-oxygen burners.
 10. A multichambered steel making apparatusaccording to claim 2, wherein each smelting chamber comprises twogas-oxygen burners.
 11. A multichambered steelmaking apparatus,comprising: at least two smelting chambers communicating with eachother; each said smelting chamber comprising a roof, a hearth, an outletarranged on a side of a chamber back wall, a set of side walls and afront wall with two input ports and a process port arranged between saidinput ports; each said smelting chamber including at least three oxygensupply tuyere installed in said roofs; a gas exhaust channel including agas-cleaning system and at least one chimney; each said smelting chamberprovided with a tilting device and means for tilting in the direction ofsaid front and back walls at an angle of up to 45° relative to avertical axis; means for moving each said tuyeres in a verticaldirection; each said smelting chamber further comprising at least twogas-oxygen burners installed on said opposite side walls of saidsmelting chambers, facing each other at an angle, and located at anangle relative a horizontal axis of said chamber; and a threshold levelof said process port being located lower than a threshold level of saidinput ports.
 12. A muitichambered steel making apparatus, according toclaim 1, wherein: said process port is narrower then respective saidinput ports.
 13. A multichambered steel making apparatus, according toclaim 1, wherein: a threshold level of said process port is lower than athreshold level of respective said input ports.
 14. A multichamberedsteelmaking apparatus, comprising: at least two smelting chamberscommunicating with each other; each said smelting chamber comprising aroof, a hearth, an outlet arranged on a side of a chamber back wall, aset of side walls and a front wall with two input ports and a processport arranged between raid input ports; each said smelting chamberincluding at least one oxygen supply tuyere installed in said roofs;means for moving said at least oxygen supply tuyere vertically relativeto respective said chamber; a gas exhaust channel including agas-cleaning system and at least one chimney; each said smelting chamberprovided with a tilting device and means for tilting in the direction ofsaid front and back walls at an angle of up to 45° relative to avertical axis; means for moving each said tuyeres in a verticaldirection; and each said smelting chamber further comprising at leasttwo gas-oxygen burners installed on said opposite side walls of saidsmelting chambers, facing each other at an angle, and located at anangle relative a horizontal axis of said chamber.
 15. A multichamberedsteelmaking apparatus, comprising: at least two smelting chamberscommunicating with each other; each said smelting chamber comprising aroof, a hearth, a outlet arranged on a side of a chamber back wall, aset of side walls and a front wall with two input ports and a processport arranged between said input ports; each said smelting chamberincluding at least one oxygen supply tuyere installed in said roofs;means for moving said at least one oxygen supply tuyere verticallyrelative to respective said chamber; a gas exhaust channel including agas-cleaning system and at least one chimney; each said smelting chamberprovided with a tilting device and means for tilting in the direction ofsaid front and back walls at an angle of up to 45° relative to avertical axis, means for moving each said tuyeres in a verticaldirection, each said smelting chamber further comprising at least twogas-oxygen burners installed on said opposite side walls of saidsmelting chambers, facing each other at an angle, and located at anangle relative a horizontal axis of said chamber; and, a threshold levelof said process port being located lower than a threshold level of saidinput ports.